Over time, it became a part of our American heritage and that of the world. The physical delivery of standard post is slow, not unlike a snail, and so “snail mail” was born. By comparison, the two or three days it can take for a letter to arrive feels like an eternity. Send an e-mail or text message, and they arrive on your recipient’s device moments later. The word “snail mail” got its name precisely because of these new messaging options. The 'snail' in snail mail is given relative to newer services. It's communication, physically delivered to its recipient. It's the conventional postal system we're all familiar with - you drop something in a mailbox and USPS mail carriers pick it up and deliver it, along with letters from millions of other people to addresses all over the world.
'Some computer users refer to conventional mail using the postal system as snail mail, because it is very slow in comparison with e-mail.' Collins English Dictionary defines it this way: What is snail mail? If you’re not familiar with the term or looking for the snail mail meaning, you almost certainly know it by its original name - the mail. Sending mail through the post office was once the only way to send and receive messages, but it’s been largely replaced by email, text messages, and chat.
